Cheese is generally made by developing acidity in milk and setting the milk with a clotting agent, such as rennet, or by developing acidity to the isoelectric point of the protein. The set milk is cut and whey is separated from the resulting curd. The curd may be pressed to provide a cheese block. The whey, which contains significant amounts of whey protein, is generally further processed for protein and fat recovery. Curing typically takes place over a lengthy period of time under controlled conditions. Process cheese-type products can be prepared from such conventional cheeses by grinding and then heating the ground cheeses with emulsifying salt or salts in, for example, a laydown cooker.
The name or label given to the resulting product depends upon the ingredients used, its composition, and, in some instances, regulations promulgated by the U.S. Food and Drug Administration 21 C.F.R. .sctn..sctn.133.169-180. For example, the term "pasteurized process cheese" refers to a product comprising a blend of cheeses to which an emulsifying agent, usually an emulsifying salt, and possibly acids, have been added, and which has then been worked and heated into a homogeneous plastic mass.
The term "pasteurized process cheese food" refers to a product which is prepared from the same materials and the same processes used for manufacture of process cheese. However, cheese food generally has added dairy ingredients such as cream, milk, skimmed milk, whey, or any of these from which part of the water has been removed (e.g., concentrated skimmed milk). The moisture level in process cheese food is generally higher than that of process cheese and may be up to about 44%. Fat is generally present at a level of not less than 23%. The term "pasteurized process cheese spread" refers to a product which is similar to cheese food, in the sense that it can contain the indicated dairy ingredients. Process cheese spread, however, may have a moisture level as high as 60%, and a minimum fat level of 20%. Process cheese, process cheese food, and process cheese spread are generally referred to as "standardized products", since their methods of manufacture and composition are determined by Federal Standards of Identity.
As used herein, the term "process cheese-type products" includes those products known and referred to as "pasteurized process cheese," "pasteurized process cheese food," "pasteurized process cheese spread," and "pasteurized process cheese product." "Process cheese-type products" also includes products resembling process cheese, process cheese food, process cheese spread, and process cheese product, regardless of whether or not they meet the U.S. Federal Standards of Identity for any of the above products in that they may contain ingredients not specified by such Standards, such as vegetable oil or vegetable protein, or may not meet the compositional requirements of such Standards. Process cheese-type products also include products having flavor and texture similar to those of a process cheese product regardless of the ingredients or manufacturing steps employed, and regardless of whether the Standards have been met.
There have been many efforts to provide simplified processes for making cheese or cheese-type products. U.S. Pat. No. 4,268,528 (May 19, 1981) provides a method for producing soft cheeses wherein milk is acidified to a pH less than 4.4 to coagulate the milk followed by ultrafiltration to produce a flowable acidified retentate containing flocculated casein. After cooling, the acidified retentate is stirred, taking care to avoid foaming, to deflocculate the flocculated casein after which rennet is added to form the cheese.
U.S. Pat. No. 4,271,201 (Jun. 2, 1981) provides a method whereby denatured whey protein is mixed with milk either before or after ultrafilitration. The resulting ultrafiltered milk is then coagulated using a lactic starter and then drained to produce a curd containing substantially the same amount of total serum protein as the original milk.
U.S. Pat. No. 4,401,679 (Aug. 30, 1983) provides a method for preparing a cheese base wherein milk is treated with ultrafiltration combined with diafiltration and evaporation. The ultrafiltered milk is innocualted with an acid culture before evaporation and acidified after evaporation to form the cheese base.
U.S. Pat. No. 4,948,599 (Aug. 14, 1990) provides a method for the continuous production of cheese using ultrafiltration. The ultrafiltered milk is cooled and acidified to a pH of 4.8 to 5.8 without coagulation. A milk coagulating enzyme or a lactic acid starter is then added and the mixture quickly heated to 25 to 84.degree. C. to form cheese curds.
U.S. Pat. No. 4,497,834 (Feb. 5, 1985) provides a simplified method of making a dairy-based food product wherein milk is first condensed to the proportion of milk solids and moisture corresponding substantially to that desired in the final product after which the concentration of lactose in the milk is reduced by hydrolysis, molecular sieving, or ultrafiltration to below about 15 percent by weight at which crystallization was reported to occur. The mixture is then gelled by heating and thereafter cooled, manipulated, and packaged using conventional techniques.
U.S. Pat. No. 5,165,945 (Nov. 24, 1992) and U.S. Pat. No. 5,330,780 (Jul. 24, 1994) describe a process for producing cheese containing whey protein. Ultrafiltered and diafiltrated milk is renneted and then heated to coagulate the mixture and deactivate the rennet. Water is then removed without removing soluble proteins to produce a cheese which contains casein and substantially all of the soluble protein in the original feed stock.
U.S. Pat. No. 5,330,773 (Jul. 19, 1994) provides a method for producing a low-fat cheese food product wherein a gelatin or gum is added to low-fat ultrafiltrated milk. The resulting milk blend is maintaining at a temperature such that gelling does not occur. After adding an activator such as lactic acid to form a paste, it is subjected to draining, brining, and ripening to form the low-fat cheese food product.
U.S. Pat. No. 5,262,183 (Nov. 16, 1993) provides a method in which a milk retentate is fermentated to a pH of about 4.8 to about 5.6 without coagulation. After adding a milk clotting enzyme in a non-coagulating amount, water is removed by evaporation to obtain a solids content of about 55 percent or higher to produce a pre-cheese. The pre-cheese is cured (generally over a three to fourteen day period) to convert at least 65 percent of kappa casein to para kappa casein.
U.S. Pat. No. 5,356,639 (Oct. 18, 1994) and U.S. Pat. No. 5,356,640 (Oct. 18, 1994) provide a method for producing cheese containing substantially all of the casein and whey protein in the starting milk using ultrafilration and diafiltration. The retentate is treated with salt to an ionic strength which prevents coagulation during fermentation and then fermented. Water is then removed the fermented concentrate by evaporation to obtain the cheese.
U.S. Pat. No. 5,554,397 (Sep. 10, 1996) provides a method for producing a cheese-type food from powdered milk. The powdered milk is produced from liquid milk by ultrafiltration, adjusting the pH of the ultrafiltered milk to 5.0 to 5.8, and then spray dried. The spray dried powdered milk, emulsifying salts, and water are heated to form a liquid mixture which is then cooled to obtain the cheese-type food.
In spite of the numerous attempts and the clear advantages such simplified processes would provide, they have generally not been commercially successful and, thus, the conventional cheese-making process remains, even with its significant drawbacks, the process of choice.
It would be desirable to provide a commercially-viable method for producing a cheese product which does not involve a whey drainage step and which can be accomplished in a short period of time. It would also be desirable to provide a commercially-viable, semi-continuous or continuous method for producing a cheese product directly from milk. It would also be desirable to provide a commercially-viable process by which milk can be converted into a storage-stable product (i.e., milk protein concentrate) which can be converted to a cheese product at a later time depending on the demand and need for the cheese product. It would also be desirable to provide a commercially-viable process whereby such storage-stable milk protein concentrate could be used to make a wide variety of cheese products including, but not limited to, full-fat, reduced-fat, and fat-free cheese products. The present specification provides such commercially-viable methods.